Latch for a fold out ramp

ABSTRACT

A latch assembly is suitable for a ramp assembly, the ramp assembly having a ramp portion coupled to a fixed portion so that the ramp portion reciprocates between a stowed position and a deployed position. The latch assembly includes a latch pin attached to the ramp portion. The latch assembly further includes a latch fitting coupled to the fixed portion of the ramp assembly. The latch fitting has a hook portion and a tang. The latch fitting selectively reciprocates between a first position, a second position, and a third position. In the first position, the hook engages the latch pin to retain the ramp portion in the stowed position. In the second position, the hook portion is disengaged from the latch pin. In the third position, the tang applies a lifting force to the ramp portion.

CROSS-REFERENCE(S) TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Application No.60/916,238, filed on May 4, 2007, and U.S. Provisional Application No.60/944,413, filed on Jun. 15, 2007, the disclosures of which areexpressly incorporated by reference.

TECHNICAL FIELD

The present disclosure relates generally to wheelchair lifts and, moreparticularly, to fold out ramps for vehicles.

BACKGROUND

The Americans with Disabilities Act (ADA) requires the removal ofphysical obstacles to those who are physically challenged. The statedobjective of this legislation has increased public awareness and concernover the requirements of the physically challenged. Consequentially,there has been more emphasis in providing systems that assist such aperson to access a motor vehicle, such as a bus or minivan.

A common manner of providing the physically challenged with access tomotor vehicles is a ramp. Various ramp operating systems for motorvehicles are known in the art. Some slide out from underneath the floorof the vehicle and tilt down. Others are stowed in a vertical positionand are pivoted about a hinge, while still others are supported by boomsand cable assemblies. The present invention is generally directed to a“fold out” type of ramp. Such a ramp is normally stowed in a horizontalposition within a recess in the vehicle floor, and is pivoted upward andoutward to a downward-sloping extended position. In the extendedposition, the ramp is adjustable to varying curb heights.

Fold out ramps on vehicles confront a variety of technical problems.Longer ramps are desirable because the resulting slope is lower and moreaccessible by wheelchair-bound passengers. Longer ramps are, however,heavier and require more torque about the pivot axis to be reciprocatedbetween deployed and stowed positions. To satisfy this torquerequirement, such fold out ramps use large electric motors, pneumaticdevices, or hydraulic actuators to deploy and stow the ramp. Many ofsuch systems cannot be moved manually in the event of failure of thepower source unless the drive mechanism is first disengaged. Someexisting fold out ramps can be deployed or stowed manually, but they aredifficult to operate because one must first overcome the resistance ofthe drive mechanism. Moreover, dirt and debris often enter an interiorportion of the ramp, causing premature wear and failure. Further, foldout ramps require a depression (or pocket) in the vehicle's vestibulefloor in which to store the retracted/stowed ramp. When the ramp isdeployed, the aforementioned depression presents an obstacle forwheelchair passengers as they transition from the ramp to the vestibule,and on into the vehicle.

As noted above, many existing fold out ramps are equipped withhydraulic, electric, or pneumatic actuating devices. Such devices areobtrusive and make access to and from a vehicle difficult when the rampis stowed. Moreover, many of such fold out ramps have no energy storagecapabilities to aid the lifting of the ramp, which would preserve thelife of the drive motor or even allow a smaller drive to be employed.Finally, operating systems for such fold out ramps must have large powersources to overcome the moment placed on the hinge by the necessarilylong moment arm of the fold out ramp.

SUMMARY

A first exemplary embodiment of a described latch assembly is suitablefor a ramp assembly having a ramp portion coupled to a fixed portion sothat the ramp portion reciprocates between a stowed position and adeployed position. The latch assembly includes a latch pin attached tothe ramp portion. The latch assembly further includes a latch fittingcoupled to the fixed portion of the ramp assembly. The latch fitting hasa hook portion and a tang. The latch fitting selectively reciprocatesbetween a first position, a second position, and a third position. Inthe first position, the hook engages the latch pin to retain the rampportion in the stowed position. In the second position, the hook portionis disengaged from the latch pin. In the third position, the tangapplies a lifting force to the ramp portion.

A second exemplary embodiment of a described latch assembly is suitablefor a ramp assembly having a ramp portion coupled to a fixed portion sothat the ramp portion reciprocates between a stowed position and adeployed position. The latch assembly includes a latch pin coupled tothe ramp portion. The latch assembly further includes a latch fittingcoupled to the fixed portion of the ramp assembly. The latch fitting hashook portion and a tang. The latch assembly also includes a latch handlecoupled to the latch fitting to reciprocate between a retracted positionand an extended position. The latch fitting is selectively movable toreciprocate between a latching position, in which the hook portionengages the latch pin to retain the ramp portion in a stowed position,and a lifting position, in which the tang applies a lifting force to theramp portion.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features ofthe claimed subject matter, nor is it intended to be used as an aid indetermining the scope of the claimed subject matter.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated by reference to thefollowing detailed description, when taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is an isometric view of an exemplary embodiment of a rampassembly, with an ramp portion in the stowed position;

FIG. 2 is an isometric view of the ramp assembly shown in FIG. 1, withthe ramp portion in a deployed position;

FIG. 3 is an isometric partial cutaway view of the ramp assembly shownin FIG. 1, with the ramp portion in a position between the stowedposition and a deployed position;

FIG. 4 is an isometric, partial cut-away view of an outboard support ofa movable floor of the ramp assembly shown in FIG. 3;

FIG. 5 is an isometric, partial cut-away view of an inboard support ofthe movable floor of the ramp assembly shown in FIG. 3;

FIG. 6 is a partial cross-sectional side view of the outboard support ofthe movable floor of the ramp assembly shown in FIG. 4, with the rampportion in the stowed position;

FIG. 7 is a partial cross-sectional side view of the outboard support ofthe movable floor of the ramp assembly shown in FIG. 4, with the rampportion positioned between the stowed position and a deployed position;

FIG. 8 is a partial cross-sectional side view of the outboard support ofthe movable floor of the ramp assembly shown in FIG. 4, with the rampportion in a deployed position;

FIG. 9 is a partial cross-sectional side view of the inboard support ofthe movable floor of the ramp assembly shown in FIG. 5, with the rampportion in the stowed position;

FIG. 10 is a partial cross-sectional side view of the inboard support ofthe movable floor of the ramp assembly shown in FIG. 5, with the rampportion positioned between the stowed position and a deployed position;

FIG. 11 is a partial cross-sectional side view of the inboard support ofthe movable floor of the ramp assembly shown in FIG. 5, with the rampportion in a deployed position;

FIG. 12 is an isometric, partial cut-away view of the ramp assemblyshown in FIG. 1, with the ramp assembly in a deployed position;

FIG. 13 is a partial side view of the ramp assembly shown in FIG. 1,with the ramp portion in a neutral position;

FIG. 14 is a partial side view of the ramp assembly shown in FIG. 1,with the ramp portion positioned between a neutral position and thestowed position;

FIG. 15 is a partial side view of the ramp assembly shown in FIG. 1,with the ramp portion positioned between a neutral position and adeployed position;

FIG. 16 is a chart showing a moment provided by a counterbalance of theramp assembly of FIG. 13;

FIG. 17 is a partial cross-sectional view of a closeout assembly of theramp assembly shown in FIG. 1, with the ramp portion in the stowedposition;

FIG. 18 is a partial cross-sectional view of the closeout assembly shownin FIG. 17, with the ramp portion positioned between the stowed positionand a deployed position;

FIG. 19 is a partial cross-sectional view of the closeout assembly shownin FIG. 17, with the ramp portion in a deployed position;

FIG. 20 is an isometric, partial cut-away view of the ramp assemblyshown in FIG. 1, with the ramp assembly in a position between the stowedposition and a deployed position;

FIG. 21 is a partial cross-sectional view of a latch assembly of theramp assembly shown in FIG. 20, with the ramp portion in the stowedposition;

FIG. 22 is a partial cross-sectional view of the latch assembly of FIG.21 during a powered unlatch operation;

FIG. 23 is a partial cross-sectional view of the latch assembly of FIG.21 during a first phase of a manual unlatch operation; and

FIG. 24 is a partial cross-sectional view of the latch assembly of FIG.21 during a second phase of a manual unlatch operation.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will now be describedwith reference to the accompanying drawings where like numeralscorrespond to like elements. Exemplary embodiments of the presentinvention are directed to ramp assemblies, and more specifically, towheelchair ramp assemblies. In particular, several embodiments of thepresent invention are directed to wheelchair ramp assemblies suitablefor use in buses, vans, etc. Several embodiments of the presentinvention are directed to compact ramp assemblies for a vehicle thatwhen stowed, occupy a small amount of space within the vehicle floor,yet deploy to a length that effectively reduces the ramp slopeencountered by the mobility impaired, thus facilitating greaterindependence and safety for wheelchair-bound passengers.

The following discussion proceeds with reference to examples ofwheelchair ramp assemblies for use in vehicles having a floor, such as abus, van, etc. While the examples provided herein have been describedwith reference to their association with vehicles, it will be apparentto one skilled in the art that this is done for illustrative purposesand should not be construed as limiting the scope of the invention, asclaimed. Thus, it will be apparent to one skilled in the art thataspects of the present invention may be employed with other rampassemblies used in stationary installations, such as residentialbuildings and the like.

The following detailed description may use illustrative terms such asvertical, horizontal, front, rear, inboard, outboard, proximal, distal,etc. However, these terms are descriptive in nature and should not beconstrued as limiting. Further, it will be appreciated that embodimentsof the present invention may employ any combination of featuresdescribed herein.

Fold Out Ramp Assembly

FIGS. 1 and 2 illustrate one embodiment of a fold out ramp assembly 20(hereinafter “ramp assembly 20”). The ramp assembly 20 includes a frame30, a drive assembly 80, an ramp portion 60, an intermediate panelassembly 70, a movable floor 40, and a counterbalance assembly 100. Theframe 30 of the ramp assembly 20 is adapted to be mounted to a vehicle(not shown) having a floor, such as a bus or a van. The ramp assembly 20is reciprocal between the stowed position, as shown in FIG. 1, and adeployed position, as shown in FIG. 2.

Although the illustrated embodiments of the ramp assembly 20 include aframe 30, other embodiments are contemplated in which the ramp assembly20 does not include a frame 30. When such embodiments are installed invehicles, the ramp assembly 20 components are attached directly to thestructure of the vehicle or to a suitable structure within the vehicle,thus making a frame 30 unnecessary. Similarly, when such embodiments areinstalled in stationary installations, such as residential buildings andthe like, the ramp assembly 20 components are attached to the structureof the building or any other suitable structure within the building.Accordingly, embodiments of the described ramp assembly 20 that do notinclude a frame, should be considered within the scope of the presentdisclosure.

Referring to FIGS. 1 and 2, the ramp portion 60 has a first end 61 and asecond end 62. When the ramp portion 60 is in the stowed position, thefirst end 61 of the ramp portion 60 is outboard of the second end 62 ofthe ramp portion 60. As the ramp portion 60 moves from the stowedposition to a deployed position, the ramp portion 60 rotates about thefirst end 61 of the ramp portion 60 until the second end 62 of the rampportion 60 is outboard of the first end 61 of the ramp portion 60.

As best shown in FIG. 1, when the ramp assembly 20 is in the stowedposition, the ramp portion 60 and the movable floor 40 are located suchthat the ramp portion 60 is positioned over the movable floor 40, andthe lower surface 66 of the ramp portion 60 is substantially parallelwith the floor (not shown) of the vehicle. In the deployed position, theramp portion 60 extends in an outboard direction and contacts a surface22, such as a curb or road side.

Referring now to FIG. 2, the ramp portion 60 is pivotally connected atthe first end 61 to the frame 30. In addition, the first end 61 of theramp portion 60 is hingedly coupled to the outboard end 74 of theintermediate panel assembly 70. The ramp portion 60 includes a panel 63,which is constructed from well-known materials. The ramp portion 60further includes side curbs 68. The side curbs 68 extend upwardly fromthe forward and rear sides of the panel 63. Each side curb 68 enhancesthe structural strength of the ramp portion 60 and provides edge guardsfor the sides of the ramp portion 60, thereby increasing the safety ofthe ramp assembly 20. The second end 62 of the ramp portion 60 includesa tapered nose portion 64. The tapered nose portion 64 provides a smoothtransition between the panel 63 and the curb or sidewalk when the rampassembly 20 is in a deployed position.

The movable floor 40 includes an inboard portion 42 fixedly located atan angle relative to a sloping outboard portion 44. When the rampportion 60 is stowed, the movable floor 40 is disposed within the frame30 and below the ramp portion 60 in a lowered position as best shown inFIGS. 6 and 9. Referring to FIGS. 6-11, as the ramp portion 60 isdeployed, the outboard portion 44 of the movable floor 40 translatesinboard and outboard in a substantially horizontal direction, while theinboard portion 42 travels upward in a substantially arcuate, clockwisepath as viewed in FIGS. 9-11.

Referring back to FIG. 2, a gap exists between the first end 61 of theramp portion 60 and the outboard end of the movable floor 40. Theintermediate panel assembly 70 bridges this gap and provides atransition surface between the ramp portion 60 and the movable floor 40.As best shown in FIGS. 3 and 4, the intermediate panel assembly 70includes a panel 78 supported at the forward and rear sides by a pair ofside supports 76.

The outboard end 74 of the intermediate panel assembly 70 is hingedlycoupled to the first end 61 of the ramp portion 60 about a first hingeaxis 34. As best shown in FIGS. 6-8, hinge pins 38 are located at theforward and rear sides of the first end 61 of the ramp portion 60 tohingedly attach the first end 61 of the ramp portion 60 to the sidesupport 76 of the intermediate panel assembly 70. The hinge pins 38 arepositioned so that the hinge axis 34 is substantially parallel to, butoffset from, the axis of rotation of the outboard sprockets 88. As aresult, the hinge axis 34, and thus the outboard end 74 of theintermediate panel assembly 70, moves in an arcuate path around thecenterline of the outboard sprocket 88 when the ramp portion 60 movesbetween the stowed position and a deployed position.

The inboard end 72 of the intermediate panel assembly 70 is hingedlycoupled to the outboard end of the movable floor 40 about a second hingeaxis 36. As best shown in FIGS. 6-8, hinge pins 56 are located along thesecond hinge axis 36 at the forward and rear sides of the outboard endof the movable floor 40 to hingedly attach the outboard end of themovable floor 40 to the side support 76 of the intermediate panelassembly 70. The second hinge axis 36 is substantially parallel to, butoffset from, the axis of rotation of the outboard sprockets 88.

When the ramp portion 60 is in a deployed position, the outboard portion44 of the movable floor 40 extends from the inboard portion 42 of themovable floor 40 in an outboard and downward direction to the outboardedge of the movable floor 40 so that the outboard portion 44 of themovable floor 40 has a slope approximately equal to the slope of theramp portion 60. The outboard portion 44 of the movable floor 40 is alsoapproximately parallel to the ramp portion 60 so that the intermediatepanel assembly 70 also has a slope similar to the outboard portion 44 ofthe movable floor 40 and to the ramp portion 60. It should beappreciated that some variations in the slopes of the ramp portion 60,the intermediate panel assembly 70, and the outboard portion 44 of themovable floor 40 may result from different distances between the floorof the vehicle and the curb or street surfaces.

As a result of the above-described configuration, the outboard portion44 of the movable floor 40 and the intermediate panel assembly 70effectively increase the overall length of the sloped portion of thedeployed ramp. Consequently, a more gradual slope is achieved withoutincreasing the length of the ramp portion 60. Because the length of theramp portion 60 is not increased, the torque required from the drivemotor 82 to reciprocate the ramp portion 60 between the stowed positionand a deployed position is not increased.

The drive assembly 80 actuates the ramp portion 60. As a result, theramp portion 60 reciprocates between the stowed position and a deployedposition. A forward portion of the drive assembly is located on theforward side of the frame 30. A rear portion of the drive assembly 80 issimilarly located on the rear side of the frame 30, wherein each elementof the forward portion of the drive assembly 80 corresponds to a similarelement of the rear portion of the drive assembly 80. For the sake ofclarity, the forward portion of the drive assembly 80 is describedherein with the understanding that unless otherwise indicated, eachelement of the forward portion has a corresponding element on the rearportion of the drive assembly 80.

Referring to the embodiment shown in FIGS. 1 and 2, the drive assembly80 includes an inboard sprocket 86 that is rotatably coupled to theinboard end of the forward side of the frame 30. The inboard sprocket 86is oriented to have an axis of rotation that extends in theforward/rearward direction. The drive assembly 80 also includes anoutboard sprocket 88 rotatably coupled to the outboard end of theforward side of the frame 30. The outboard sprocket 88 is oriented tohave an axis of rotation that is substantially parallel to the axis ofrotation of the inboard sprocket 86. A drive chain 92 forms an endlessloop that engages the teeth of the outboard sprocket 88 and the teeth ofthe inboard sprocket 86. Movement of the drive chain 92 along the pathof the drive chain 92 rotates the inboard sprocket 86 and the outboardsprocket 88.

The drive assembly 80 further includes drive sprocket 84 rotatablycoupled to the forward side of the frame 30 intermediate to the inboardsprocket 86 and outboard sprocket 88. The drive sprocket 84 is orientedto have an axis of rotation substantially parallel to the axes ofrotation of the inboard sprocket 86 and outboard sprocket 88. As shownin FIG. 12, a drive shaft 83 is coupled to the drive sprocket 84 forconnecting the drive sprocket 84 to a motor 82, wherein the drive shaft83 is operatively coupled to the motor 82 by a well known transmissionmeans 85. The motor 82 is selectively operated to rotate the drivesprocket 84, thereby driving the inboard sprocket 86 and the outboardsprocket 88 via the drive chain 92. In one embodiment, a single motor 82drives the drive sprocket 84 of the forward portion of the driveassembly 80 and also the drive sprocket 84 of the rear portion of thedrive assembly 80. In another embodiment, each drive sprocket 84 isdriven by a separate motor 82.

One or more idler sprockets 90 may be included in the drive assembly 80.The optional idler sprockets 90 engage the drive chain 92 to redirectthe drive chain 92 along a predetermined path. The drive chain 92includes a turnbuckle 98 that is selectively adjustable to increase ordecrease the length of the drive chain 92 in order to adjust the tensionof the drive chain 92.

As illustrated in FIGS. 6-11, the inboard sprockets 86 and outboardsprockets 88 of the drive assembly 80 rotate cooperatively toreciprocate the ramp assembly 20 between the stowed position and adeployed position. More specifically, the outboard sprockets 88 rotateto reciprocate the ramp portion 60 between the stowed position and adeployed position. At the same time, the inboard sprockets 86 andoutboard sprockets 88 cooperate to arcuately raise and lower, andhorizontally translate the movable floor 40 as the ramp portion 60reciprocates between the stowed position and a deployed position.

Actuation of the Ramp Portion

FIGS. 6-8 illustrate the outboard sprocket 88 as it drives the rampportion 60 from the stowed position (FIG. 6), through an intermediateposition (FIG. 7), to a deployed position (FIG. 8). Referring to FIG. 6,a portion of the outboard sprocket 88 extends through the frame 30 toact as a ramp support element. The ramp portion 60 is fixedly attachedto a portion of the outboard sprocket 88 that extends axially throughthe frame 30 into the interior portion of the frame 30. The lowersurface 66 of the ramp portion 60, which faces up when the ramp assembly20 is in the stowed position, is offset from the axis of rotation of theoutboard sprocket 88 so that the lower surface 66 is generallyhorizontal and coplanar with the floor of the vehicle when the rampassembly 20 is in the stowed position.

To move the ramp portion 60 from the stowed position to a deployedposition, the outboard sprocket 88 is driven by the drive assembly 80 torotate in a counterclockwise direction as viewed in FIG. 7 (i.e., thedirection of the arrow shown in FIG. 7). The ramp portion 60 rotateswith the outboard sprocket 88 until the tapered nose 64 of the rampportion 60 contacts a surface 22 of the road or sidewalk, at which pointthe ramp portion 60 is in a deployed position.

Conversely, to move the ramp portion 60 from a deployed position to thestowed position, the drive assembly 80 rotates the outboard sprocket 88in a clockwise direction as viewed in FIG. 7 (i.e., the directionopposite the arrow shown in FIG. 7). The ramp portion 60 rotates withthe outboard sprocket 88 until the lower surface 66 of the ramp portion60 is generally horizontal and coplanar with the floor of the vehicle,at which point the ramp portion 60 is in the stowed position. In thestowed position, the ramp portion is supported at its edges by the frame30 or the vehicle floor. By selectively operating the motor 82 of thedrive assembly 80, the ramp portion 60 is reciprocated between thestowed position and a deployed position.

Actuation of the Movable Floor

i. Outboard End

As best shown in FIGS. 6-8, the outboard end of the movable floor 40travels along a generally horizontal path in the inboard/outboarddirection as the outboard sprocket 88 rotates to move the ramp portion60 between the stowed position and a deployed position. A roller bearing52 is rotatably mounted to the frame 30 and positioned within the frame30 to contact a bearing surface 54 located on the outboard portion 44 ofthe movable floor 40. The bearing surface 54 is located on a lowersurface of the movable floor 40 so that the roller bearing 52 contactsthe bearing surface 54 from below, thereby providing support to theoutboard end of the movable floor 40 in a vertical direction.

As shown in FIG. 6, when the ramp portion 60 is in the stowed position,the hinge pin 38 connecting the ramp portion 60 to the intermediatepanel assembly 70 is located above the axis of rotation of the outboardsprocket 88. Referring to FIGS. 7 and 8, when the outboard sprocket 88rotates, the hinge axis 34 of the hinged connection between the rampportion 60 and the intermediate panel assembly 70 moves in an arcuatepath around the axis of rotation of the outboard sprocket 88. Thismotion drives the outboard end 74 of the intermediate panel assembly 70,which, in turn, drives the inboard end 72 of the intermediate panelassembly 70. The movement of the inboard end 72 of the intermediatepanel assembly 70 drives the outboard portion 44 of the movable floor40, which is supported in a vertical direction by the roller bearing 52.

When the ramp portion 60 is moved from a deployed position to the stowedposition, the hinge pin 38 moves in a clockwise direction, driving theintermediate panel assembly 70 and the outboard portion 44 of themovable floor 40 in the reverse direction of the path traveled when theramp portion 60 is being deployed.

ii. Inboard End

FIGS. 9-11 illustrate the inboard sprocket 86 as it raises the inboardend of the movable floor 40 as the ramp portion 60 moves from the stowedposition (FIG. 9), through an intermediate position (FIG. 10), to adeployed position (FIG. 11). Referring to FIG. 9, a first end of a link94 is fixedly coupled to the inboard sprocket 86. The link 94 extendsradially from the inboard sprocket 86 so that the second end of the link94 revolves around the axis of rotation of the inboard sprocket 86 asthe inboard sprocket 86 is rotated by the drive assembly 80. A followerbearing 96 is rotatably coupled to the second end of the link 94 so thatthe axis of rotation of the follower bearing 96 is approximatelyparallel to the axis of rotation of the inboard sprocket 86. Thefollower bearing 96 travels in an arcuate path around the axis ofrotation of the inboard sprocket 86 when the drive assembly 80 drivesthe inboard sprocket 86. The inboard sprocket 86, the link 94, and thefollower bearing 96 cooperate to function as a reciprocating mechanismto reciprocate the inboard end of the movable floor 40 between a raisedposition and a stowed position.

A side support 46 extends along the lower edge of the movable floor 40from the inboard end of the movable floor 40 to the outboard end of themovable floor 40. The side support 46 includes a protrusion that extendsfrom the inboard portion of the side support 46 in an outboard anddownward direction to form a C-shaped catcher 48. The catcher 48 openstoward the outboard end of the ramp assembly 20. The lower portion ofthe side support that is located outboard of the catcher 48 includes abearing surface 50.

As shown in FIG. 9, when the ramp portion 60 is in the stowed position,the link 94 extends downward from the inboard sprocket 86. As a result,the follower bearing 96 is positioned below the axis of rotation of theinboard sprocket 86. The follower bearing 96 engages the bearing surface50 of the side support 46, thereby supporting the inboard end of themovable floor 40. If external forces tend to raise the inboard end ofthe movable floor 40, the follower bearing 96 engages the catcher 48,thereby preventing the side support 46, and therefore the movable floor40, from moving in an upward direction. The catcher 48 also restrainsthe movable floor 40 to reduce unwanted noise and vibration when thevehicle is in motion.

Referring to FIG. 10, when the ramp portion 60 moves from the stowedposition to a deployed position, the inboard sprocket 86 rotates in aclockwise direction. As the follower bearing 96 travels along an arcuatepath as a result of the motion of the inboard sprocket 86, the followerbearing 96 maintains contact with the bearing surface 50. Thus, thefollower bearing 96 provides continuous support to the inboard end ofthe movable floor 40 as the follower bearing 96 travels along an arcuatepath, thereby raising the inboard end of the movable floor 40.

FIG. 11 shows the inboard end of the movable floor 40 when ramp portion60 is in a deployed position. The follower bearing 96 is generallypositioned above the axis of rotation of the inboard sprocket 86 and isdisposed within the catcher 48. The follower bearing 96 supports theside support 46 of the movable floor 40 so that the upper surface of themovable floor 40 is generally horizontal and coplanar with the floor ofthe vehicle.

When the ramp portion 60 is moved from a deployed position to the stowedposition, the inboard sprocket 86 rotates in a counterclockwisedirection as viewed in FIG. 10 (i.e., the direction opposite the arrowsshown in FIG. 10), and the follower bearing 96 travels in a downwardarcuate path. The inboard end of the movable floor 40, which issupported by the follower bearing 96, travels downward with the followerbearing 96 until the ramp portion 60 is in the stowed position. When theramp portion 60 is in the stowed position, the inboard end of themovable floor 40 is disposed within the frame 30 in a lowered position.

As previously discussed, the drive chain 92 coordinates the rotation ofthe inboard sprocket 86 and the outboard sprocket 88. Accordingly, theinboard sprocket 86 and the outboard sprocket 88 cooperate to controlthe position of the movable floor 40.

When the ramp portion 60 is in a deployed position, the sloped portionof the ramp assembly 20 has a slope defined as ratio of the height(rise) of the sloped portion to the horizontal length (run) of thesloped portion. To provide a slope that is gradual enough to allow safeingress to and egress from the vehicle by a person in a wheelchair, theratio of rise to run is generally no greater than 1:4. Smaller ratios,such as 1:5, 1:6, and 1:7 are preferable from a safety standpoint, butgiven vehicle floor height constraints, smaller ratios generally requirelonger ramps, which result in larger actuation motors and more spacerequired within the vehicle to stow the ramps. Although embodiments arenot limited to any particular ratio, a ratio of 1:6 has been found toprovide a balance between the increased safety of a more gradual slopeand the design constraints inherent in a longer ramp.

Counterbalance Assembly

FIG. 13 illustrates the ramp portion 60 in a position between the stowedposition and a deployed position. In the illustrated position, the rampportion 60 forms an angle of approximately 90° with the frame 30. Thecenter of gravity (CG) of the ramp portion 60 is located approximatelyover the axis of rotation of the outboard sprocket 88 when the rampportion is in this “neutral” position. In the illustrated embodiments,the weight of the ramp is idealized as a point load W applied at the CGof the ramp portion 60. When the ramp portion 60 is in the neutralposition, the weight of the ramp portion 60 does not impart a momentM_(W) about the axis of rotation of the outboard sprocket 88. FIG. 14shows the ramp portion 60 at a position between the neutral position andthe stowed position. When the ramp portion is so positioned, the CG ofthe ramp portion 60 is located inboard of the axis of rotation of theoutboard sprocket 88. Accordingly, the weight W of the ramp portion 60imparts moment M_(W) about the axis of rotation of the outboard sprocket88, wherein the moment M_(W) tends to move the ramp portion 60 towardthe stowed position. FIG. 15 shows the ramp portion 60 at a positionbetween the neutral position and a deployed position. In this position,the CG of the ramp portion 60 is located outboard of the axis ofrotation of the outboard sprocket 88. As a result, the weight W of theramp portion 60 imparts moment M_(W) about the axis of rotation of theoutboard sprocket 88, wherein the moment M_(W) tends to move the rampportion toward a deployed position. Although the neutral position isillustrated as a position wherein the ramp portion 60 is positioned anangle of approximately 90° from the frame 30, it should be understoodthat the position of the CG of the ramp portion 60 can vary, resultingin a neutral position wherein the angle of the ramp portion to the frame30 is greater than or less than 90°.

As shown in FIGS. 13-15, the ramp assembly 20 may include acounterbalance assembly 100 to counteract the moment M_(W) impartedabout the axis of rotation of the outboard sprocket 88 by the weight ofthe ramp. The counterbalance assembly provides a moment M_(F) thatopposes the moment M_(W) produced by the ramp portion 60. Because themoment M_(W) is counteracted by the moment M_(F) provided by thecounterbalance assembly 100, the torque output required from the motor82 of the drive assembly 80 is reduced. The reduced torque requirementallows for the use of a smaller motor 82.

In the embodiment illustrated in FIGS. 13-15, the counterbalanceassembly 100 includes an upper spring assembly 102 and a lower springassembly 122 on each of the forward and rear sides of the ramp assembly20, for a total of four spring assemblies. For the sake of clarity, theupper and lower spring assemblies 102, 122 located on the forward sideof the ramp assembly 20 are described with the understanding thatsimilar upper and lower spring assemblies 102, 122 are located on therear side of the ramp assembly 20.

Referring to FIG. 13, the upper and lower spring assemblies 102, 122 areattached in series to segments of the drive chain 92. More specifically,the outboard end of the upper spring assembly 102 is coupled to theupper end of an outboard chain segment 118, and the inboard end of theupper spring assembly 102 is coupled to the upper end of an inboardchain segment 120. The outboard end of the lower spring assembly 122 iscoupled to the lower end of the outboard chain segment 118, and theinboard end of the lower spring assembly 122 is coupled to the lower endof the inboard chain segment 120. In this manner, a drive chain isformed into an endless loop, wherein the loop comprises the followingcomponents in order: outboard chain segment 118, upper spring assembly102, inboard chain segment 120, and lower spring assembly 122.

The lower spring assembly 122 includes a rigid rod 114 positioned in aninboard/outboard orientation. The outboard end of the rod 114 is coupledto the lower end of the outboard chain segment 118 with a pinnedconnection at 124A. Similarly, the inboard end of the rod 114 is coupledto the lower end of the inboard chain segment 120 with a pinnedconnection at 124B. A helical compression spring 104 is concentricallyarranged with respect to the rod 114 so that the rod 114 is disposedwithin the center of the coils of the spring 104.

The lower spring assembly 122 further includes a spring fitting 106A, acylindrical bushing 108A, and an adjustment nut 112A associated with theoutboard end region of the rigid rod 114. The spring fitting 106A has anaperture with a diameter larger than the outer diameter of the rod 114,but smaller than the outer diameter of the compression spring 104. Thespring fitting 106A is slidingly coupled to the outboard end of the rod114 so that the rod passes through the aperture of the spring fitting106A. The cylindrical bushing 108A (biasing element) is coupled to therod 114 so that a portion of the rod 114 is disposed within the bore ofthe bushing 108A. Thus, the outboard end of the compression spring 104bears against the inboard surface the spring fitting 106A, and theoutboard surface of the spring fitting 106A bears against the inboardsurface of the cylindrical bushing 108A. The adjustment nut 112Athreadedly engages a threaded portion of the outboard end of the rod114. The inboard end of the adjustment nut 112A engages the outboard endof the cylindrical bushing 108A, preventing the cylindrical bushing108A, the spring fitting 106A, and the outboard end of the compressionspring 104 from moving in an outboard direction relative to the rod 114.

Similar to the outboard end of the rod 114, a spring fitting 106B, abushing 108B, and an adjustment nut 112B are attached to the inboard endof the rod 114. That is, the spring fitting 106B is installed inboard ofthe compression spring 104, the bushing 108B (biasing element) isinstalled inboard of the spring fitting 106B, and the adjustment nut112B installed inboard of the bushing 108B.

Still referring to FIG. 13, the compression spring 104 of the describedlower spring assembly 122 is compressed between the two spring fittings106A-B. The combination of the spring fittings 106A-B, bushings 108A-B,and nuts 112A-B prevents the compressed spring from expanding in eitherthe inboard or outboard direction. Further, the preload on thecompressed spring 104 can be adjusted by selectively adjusting thedistance between the adjustment nuts 112A-B. As the distance between thenuts 112A-B is decreased, the spring 104 is further compressed,increasing the preload on the spring 104. Conversely, if the distancebetween the nuts 112A-B is increased, the spring 104 expands, and thepreload on the spring 104 is decreased.

The compression spring 104 and spring fittings 106A-B are disposedbetween the inboard and outboard end stops 110A-B. Each end stop 110A-Bincludes a pair of protrusions to define a channel therebetween. Eachchannel is positioned in the direction of the compression spring and issized to allow the bushings 108A-B and adjustment nuts 112A-B to passtherethrough. The spring fittings 106A-B, however, are sized so as notto pass through the channels, but instead remain disposed between theinboard and outboard end stops 110A-B.

The upper spring assembly 102 is identical to the lower spring assembly122 with one exception. In the illustrated embodiment shown in FIGS.13-15, the inboard end of the rod 114 is coupled to one end of aturnbuckle 98. The other end of the turnbuckle 98 is coupled to theupper end of the inboard chain segment 120. The tension of the drivechain 92 is selectively adjustable by rotating the turnbuckle 98.Although the turnbuckle 98 is illustrated attached to the inboard end ofthe upper spring assembly 102, it should be understood that theturnbuckle can be located at any position along the path of the drivechain 92 that does not interfere with the spring assemblies 102, 122 orthe sprockets of the drive assembly 80.

FIG. 14 shows the ramp assembly 20 with the ramp portion 60 locatedbetween a neutral position and the stowed position. As the ramp portion60 moves toward the stowed position, the CG of the ramp portion movesinboard, imparting a moment M_(W) that tends to move the ramp portion 60into the stowed position. Moreover, as the ramp portion 60 moves furthertowards the stowed position, the horizontal distance between the axis ofrotation of the ramp portion 60 and the CG of the ramp portion 60increases, thus increasing the magnitude of the moment M_(W) on theoutboard sprocket 88.

The moment M_(W) imparted by the weight W of the ramp portion 60 iscounteracted by compression of the springs 104 of the upper and lowerspring assemblies 102, 122. Referring to FIG. 14, as the ramp portion 60moves toward the stowed position, the drive chain 92 moves in aclockwise direction along its path. With regard to the upper springassembly 102, the clockwise motion of the drive chain 92 drives theoutboard adjustment nut 112A, which is threadedly secured to the rod114, in an inboard direction. As the nut 112A moves inboard, it drivesthe bushing 108A and the spring fitting 106A inboard, creating a gap 116between the outboard end of the spring fitting 106A and the inboard endof the end stop 110A. The inboard end of the spring fitting 106A bearsagainst the outboard end of the compression spring 104 so that theoutboard end of the compression spring 104 moves inboard with the springfitting 106A. At the inboard end of the upper spring assembly 102, thebushing 108A and the adjustment nut 112A move inboard with the drivechain 92 and the rod 114. The spring fitting 106B, and therefore theinboard end of the compression spring 104, are prevented from movinginboard by the inboard end stop 110B.

As described above, movement of the ramp portion 60 from a neutralposition to the stowed position causes the outboard end of the uppercompression spring 104 to move inboard, while the inboard end remainsfixed against the inboard end stop 110B. The resulting compression ofthe spring 104 creates a force that, combined with the forces created bythe other springs, imparts the moment M_(F) to resist the moment M_(W)that results from the weight W of the ramp portion 60. The resistiveforce is approximately proportional to the amount by which the spring104 is compressed, i.e., the spring is a linear spring. That is, greaterspring compression results in a greater resistive force. As previouslynoted, the moment M_(W) increases as the ramp portion 60 approaches thestowed position from a neutral position. The resistive force supplied bythe spring 104 and therefore, the moment M_(F) created by the springresistive force, also increase as the ramp portion 60 approaches thestowed position. The increase in the moment M_(W) is sinusoidal, whilethe increase in the moment M_(F) is linear. As described below infurther detail, the counterbalance assembly 100 can be configured suchthat M_(F) more closely approximates M_(W) as the ramp reciprocatesbetween the stowed position and a deployed position.

The springs 104 of the counterbalance assembly 100 are preferablyselected to minimize the difference between the force supplied by thesprings 104 and the force required to counteract the moment M_(W) as theramp portion 60 reciprocates between a stowed position and a deployedposition. For linear springs, the spring stiffness can be selected suchthat the linear increase in spring resistance is a best fit of thesinusoidal increase of the moment M_(F). As a result, the differencebetween M_(W) and M_(F)is minimized. In other embodiments, non-linearsprings are used so that the resistance supplied by the spring increasesat a non-linear rate, allowing the spring resistance to match moreclosely the force required to resist the moment M_(F) as the rampportion 60 reciprocates between a stowed position and a deployedposition. Non-linear springs are known in the art. For example, a springformed with a variable coil pitch will exhibit non-linear properties. Itshould be understood that various known spring configurations providinglinear or non-linear reactive force can be included in thecounterbalance assembly 100 without departing from the spirit and scopeof the present invention. In addition, alternate systems can be used toprovide a resistive force, such as pneumatic systems, hydraulic systems,and other systems known in the art.

The lower spring assembly 122 functions in the same manner as the upperspring assembly 102. As the ramp portion 60 moves from a neutralposition to the stowed position, the inboard spring fitting 106B movesoutboard to compress the spring 104 against the outboard spring fitting106A, which is prevented from moving in the outboard direction by theoutboard end stop 110A. The compression of the spring 104 results in aforce that resists the moment M_(W) resulting from the weight of theramp portion 60.

The resistive forces produced by the upper and lower spring assemblies102, 122 act on the drive chain 92 in a direction opposite to the momentM_(W). As the moment M_(W) shown in FIG. 14 tends to move the drivechain 92 in a clockwise direction, the resistive forces produced by theupper and lower spring assemblies 102, 122 impart a moment M_(F) thattends to move the drive chain in a counterclockwise direction. To theextent that the resistive forces counteract the moment M_(W), the torquerequired from the motor 82 to drive the drive assembly 80 is reduced.

FIG. 15 illustrates the ramp assembly 20 with the ramp portion 60located between a neutral position and a deployed position. The CG (notshown) of the ramp portion 60 is located outboard of the axis ofrotation of the ramp portion 60, creating a moment M_(W) that tends tomove the ramp portion 60 into the deployed position. The upper and lowerspring assemblies are compressed in a similar fashion as discussed withrespect to FIG. 14, but in an opposite direction. More specifically, asthe moment M_(W) tends to move the drive chain 92 in a counterclockwisedirection, the upper and lower spring assemblies 102, 122 provideresistive forces that create a moment M_(F) that tends to move the drivechain in a clockwise direction.

As previously noted, upper and lower spring assemblies 102, 122 arepositioned on the forward and rear sides of the ramp assembly 20. Thefour spring assemblies cooperate to provide the moment M_(F) thatresists the moment M_(W) created when the ramp is not in a neutralposition, with each spring assembly providing approximately one fourthof the total resistive force.

The counterbalance assembly 100 can be configured so that the differencebetween the moment M_(F) and the moment M_(W) is minimized. Morespecifically, the preload in the springs 104, and the contact betweenthe spring fittings 106A-B and the end stops 110A-B can be controlled sothat the moment M_(F) is not linear, but instead approximates thesinusoidal increase and decrease of the moment M_(W).

Referring to FIG. 13, the illustrated counterbalance assembly 100includes a lower spring assembly 122, wherein the inboard and outboardspring fittings 106A-B do not contact the end stops 110A-B when the rampportion 60 is in the neutral position. As a result, a dead space 126exists between the each spring fitting 106A-B and its respective endstop 110A-B. As the ramp portion 60 initially moves from the neutralposition toward the stowed position, the outboard spring fitting 106Amoves toward the outboard end stop 110A, reducing the amount of deadspace 126. After the outboard spring fitting 106A contacts the outboardend stop 110A, the lower spring assembly begins to provide a resistiveforce. Similarly, when the ramp portion 60 moves from the neutralposition toward a deployed position, the inboard spring fitting 106Btravels toward the inboard end stop 110B. Only after the dead space 126has been eliminated, i.e. when the inboard spring fitting 106B contactsthe inboard end stop 110B, does the lower spring assembly 122 provide aresistive force.

The preload in the spring assemblies 102, 122 can be adjusted byselectively adjusting the nuts 112A-B to control compression of thesprings 104. However, adjusting the preload in this manner alsointroduces dead space into the spring assemblies 102, 122. The preloadin the spring assemblies 102 and 122 can also be adjusted independent ofthe dead space 126. In the illustrated embodiment, the spring fittings106A-B are shown as flanged bushings. By increasing or decreasing thelength of the cylindrical portion of the bushings, the space between thespring fittings, and thus, the preload on the spring 104 can becontrolled independent of the distance from the bushing flange to itsrespective end stop 110, which defines the dead space.

By adjusting the amount of dead space 126 and preload on the upper andlower spring assemblies 102 and 122, the moment M_(F) can be made tomore closely approximate the moment M_(W) produced by the weight of theramp. FIG. 16 is a chart illustrating the moment M_(F) produced by theexemplary ramp assembly 20 illustrated in FIGS. 13-15 as the rampassembly 20 reciprocates between the stowed position and a deployedposition. A line representing the moment M_(F) that is a linear best fitof the moment M_(W) is also shown. The linear best fit represents themoment M_(F) produced when the springs 104 have a zero preload, and nodead space 126 exists at the neutral position.

The chart shown in FIG. 16 further includes a series of linesrepresenting an exemplary moment M_(F) produced when a dead space 126exists on the lower spring assembly 122, but not on the upper springassembly 102. When the ramp portion 60 is at or near the neutralposition, only the upper spring assembly 102 contributes to the momentM_(F). As the ramp portion 60 moves toward the stowed position or adeployed position, the lower spring assembly is engaged, and the momentM_(F) increases more rapidly, as shown by the increased slope of theline in the areas where both the upper and lower spring assemblies 102and 122 are engaged. Further, the vertical discontinuities in the graphare achieved by preloading the springs 104 with adjustment nuts 112A-B.

As demonstrated in the exemplary embodiment of FIGS. 13-16, the momentM_(F) supplied by the counterbalance assembly 100 can be controlled tomore closely approximate the moment M_(W) imparted by the weight W ofthe ramp portion 60. It should be appreciated that each spring assembly102, 122 may include a dead space 126 at one end, both ends, or neitherend. Further, preload in the upper and lower springs 104 may differ asrequired in order to provide a moment M_(F) that more closelyapproximates the moment M_(W).

Closeout Assembly

Referring to FIGS. 17-19, the ramp assembly 20 is provided with acloseout assembly 140 located at the outboard end of the frame 30. Thecloseout assembly 140 limits access to the interior portion of the frame30 at the outboard end, thereby reducing the amount of dirt and debristhat can make its way into the interior portion of the frame 30. Thisdecreases wear of the ramp assembly 20 components. The closeout assembly140 also provides a step edge when the ramp portion 60 is in the stowedposition, and people enter and exit the vehicle on foot.

The closeout assembly 140 includes an end cap 142 that extends in aforward and rear direction to cover at least partially the outboard endof the frame 30 when the ramp portion 60 is in the stowed position. Theend cap 142 includes a horizontal, upward facing surface, which acts asa step edge, and a vertical, outboard facing surface. An upper end ofthe end cap 142 is hingedly connected to the first end 61 of the rampportion 60 along a hinge axis 154 that is approximately parallel to theaxis of rotation of the outboard sprocket 88 when the ramp portion 60 isin the stowed position. The closeout assembly 140 further includes alink 144 that is pivotally coupled at one end to a lower end of the endcap 142 along a hinge axis 155. The other end of the link 144 ispivotally coupled to the side support 76 of the intermediate panelassembly 70 along a hinge axis 156.

Referring to FIG. 17, a hinged panel assembly 146 spans a space betweenthe end cap 142 and the lower portion of the outboard end of the frame30. The hinged panel assembly 146 includes a first panel 148 hingedlycoupled at a first end to a bottom portion of the end cap 142 alonghinge axis 155. A second panel 150 is hingedly coupled at a first end toa second end of the first panel 148 along hinge axis 157. A second endof the second panel 150 is hingedly coupled to a lower portion of theoutboard end of the frame along hinge axis 158. The hinge axes 154, 155,156, 157, and 158 are approximately parallel to the axis of rotation ofthe outboard sprocket 88. Further, although the illustrated embodimentshows the link 144 connected to the end cap fitting 142 along hinge axis155, it should be appreciated that the hinged connection between thelink 144 and the end cap fitting 142 need not have a hinge axiscoincident to hinge axis 155, but can instead have a hinge axis that isoffset from hinge axis 155.

As the ramp portion 60 moves from the stowed position (FIG. 17), inwhich the closeout assembly 140 is in a closed position, through theneutral position (FIG. 18) to a deployed position (FIG. 19), in whichthe closeout assembly 140 is in an open position, the upper end of theend cap 142 moves in an arcuate path around the centerline of theoutboard sprocket 88. The motion of the ramp portion 60 also drives thelower end of the end cap 142 via the link 144 so that the end cap 144moves around the axis of the outboard sprocket 88 and out of the path ofthe ramp portion 60 to a position generally below the intermediate panelassembly 70. At the same time, the hinge axis 157 between the firstpanel 148 and the second panel 150 travels along an arcuate path to aposition under the frame 30. As a result, as shown in FIGS. 17-19, thehinged panel assembly 146 folds about the hinge axis 157 between thefirst panel 148 and second panel 150, while moving out of the path ofthe end cap 142 to a position below the frame 30.

Latch Assembly

Referring to FIGS. 20-24, a latch assembly 160 is located at the inboardend of the ramp assembly 20. The latch assembly 160 engages the rampportion 60 when the ramp assembly 20 is in the stowed position to securethe ramp relative to the frame 30. In the described embodiment, thelatch assembly 160 also includes features to assist an operator withmanual deployment of the ramp assembly 20.

As shown in FIG. 21, the latch assembly 160 includes a latch fitting 162pivotally coupled to the frame 30 with a pivot pin 164. In theillustrated embodiment, the latch fitting 162 and pivot pin 164 arepositioned so that the latch fitting 162 is rotatable about an axisextending in the forward and rear directions, however other orientationsare possible and should be considered within the scope of thedisclosure.

The latch fitting 162 includes a hook portion 166. When the ramp portion60 is in the stowed position, the hook portion 166 engages a latch pin168, which extends from the ramp portion 60. In this first position(latched position), engagement of the hook portion 166 with the latchpin 168 maintains the ramp portion 60 in the stowed position. A spring170 is connected at one end to the latch fitting 162 and at the otherend to the frame 30. When the latch fitting 162 rotates to disengage thehook portion 166 from the latch pin 168, the spring 170 is extended. Asa result, the spring 170 provides a force that tends to rotate the latchfitting 162 back toward the position in which the hook portion 166engages the latch pin 168.

Referring to FIG. 20, the latch assembly 160 is selectively operated byan actuator 172. In the illustrated embodiment, the actuator 172 is asolenoid disposed within the frame 30. The actuator 172 has an outputshaft 174 coupled to a push bar 176 with an actuation bar fitting 178.The push bar 176 is also coupled to the latch fitting 162. When theactuator 172 is actuated, the output shaft 174 of the actuator 172retracts, moving the push bar 176 in an outboard direction. The motionof the push bar rotates the latch fitting 162 to a second position(unlatched position), shown in FIG. 22, wherein the hook portion isdisengaged from the latch pin 168. With the hook portion 166 disengagedfrom the latch pin 168, the ramp portion 60 is free to move away fromthe stowed position.

A tang 180 extends from the latch fitting 162 so that the tang 180 ispositioned below a side curb 68 of the ramp portion 60. When the latchfitting 162 rotates to a third position (lifting position) shown in FIG.24, the tang 180 travels upward in an arcuate path toward the side curb68. The tang 180 contacts the side curb 68, and continues to travelalong the arcuate path, thereby imparting a lifting force on the rampportion 60.

Referring back to FIG. 21, a latch handle 182 is rotatably coupled tothe latch fitting 162 with a pivot pin 184. Rotation of the latch handle182 relative to the latch fitting 162 is limited by a retainer pin 186that is attached to the latch fitting 162. The latch handle 182 isrotatable in a first direction relative to the latch fitting 162 untilthe retainer pin 186 engages a first recess 188 in the latch handle 182,thereby defining a retracted position. Engagement of the retainer pin186 with the first recess 188 prevents further rotation of the latchhandle 182 in the first direction relative to the latch fitting 162.Similarly, the latch handle 182 is rotatable in a second directionrelative to the latch fitting 162 until the retainer pin 186 engages asecond recess 190 in the latch handle 182, thereby defining an extendedposition. A torsion spring 192 is configured to act as a biasing member,applying a biasing force that tends to position the latch handle 182 inthe retracted position.

In the illustrated embodiment, the latch handle 182 is disposed within aslot 194 so that the upper surface of the latch handle 182 issubstantially parallel with the exposed upper surface of the rampassembly 20. Sufficient space is provided to enable an operator torotate the latch handle 182 by lifting up on the outboard edge of thelatch handle 182.

The latch assembly 160 further includes a sensor 196 for sensing theposition of the ramp portion 60. In the illustrated embodiment, thesensor 196 is a limit switch; however, it should be appreciated thatvarious other sensors, such as proximity sensors, inclinometers, or anyother suitable sensor for detecting ramp position may be used. When theramp portion 60 is in the stowed position, the side curb 68 or someother feature of the ramp portion 60 engages limit switch 196. As theramp portion 60 moves from the stowed position toward a deployedposition, the ramp portion 60 disengages the limit switch 196.Disengagement of the limit switch 196 interrupts the supply of power tothe actuator 172. With power to the actuator 172 interrupted, the spring170 rotates the latch fitting 162 back to the position that the latchfitting 162 occupies when the latch fitting 162 engages the latch pin168. Disengagement of the limit switch 196 also activates the vehicleinterlock system. As a result, the vehicle is prevented from movingunless the ramp portion 60 is in the stowed position.

FIG. 22 shows the latch assembly 160 in the unlatched position during apowered unlatch operation. During the powered unlatch operation, theactuator 172 actuates the push bar 176, which rotates the latch fitting162 in a clockwise direction as viewed in FIG. 22. Rotation of the latchfitting 162 disengages the hook portion 166 from the latch pin 168. Atthe same time, the tang 180 contacts the side curb 68 of the rampportion 60 to provide a lifting force that assists the drive assembly 80in moving the ramp portion 60 from the stowed position. As the rampportion moves away from the stowed position, the ramp portion 60disengages the limit switch 196, thereby interrupting power to theactuator 172 and engaging the vehicle interlock system. With power tothe actuator 172 interrupted, the latch fitting 162 returns to itsoriginal position due to the force provided by the spring 170.

When the ramp portion 60 returns to the stowed position, the latch pin168 engages an upper surface of the hook portion 166 to rotate the latchfitting 162 out of the way of the latch pin 168. When the ramp portion60 reaches the stowed position, the latch fitting 162 rotates back dueto the force applied by the spring 170 so that the hook portion 166engages the latch pin 168, thereby securing the ramp portion 60 in thestowed position.

FIGS. 23 and 24 show the latch assembly 160 during a manualunlatch/lifting operation. An operator first pulls upwardly on anoutboard end of the latch handle 182 to rotate the latch fitting 162into the unlatched position shown in FIG. 23. Pulling on the latchhandle 182 rotates the latch handle 182 until the retainer pin 186engages the second recess 190 in the latch handle 182. With the retainerpin 186 engaging the second recess 190, continuing to pull on the latchhandle 182 rotates the latch fitting 162 until the latch fitting is inthe unlatched position.

The operator continues to pull on the latch handle 182, thereby rotatingthe latch fitting 162 to the lifting position shown in FIG. 24. In thelifting position, the tang 180 has rotated in an upward direction tocontact the ramp portion 60. As the latch fitting 162 moves to thelifting position, the tang 180 applies a lifting force to raise the rampportion 60. When the latch fitting 162 reaches the lifting position, theramp portion 60 is raised a sufficient distance to provide access forthe operator to grasp the ramp portion 60 and manually rotate the rampportion 60 to a deployed position.

In the illustrated embodiment, a latch fitting 162 is positioned at boththe forward and rear sides of the frame 30. Both latch fittings 162 areactuated by a single actuator 172. It should be appreciated thatalternate embodiments are possible wherein a single latch fitting 162 islocated at a forward, rear, or intermediate portion of the frame 30.Alternately, multiple actuators 172 may be included so that eachactuator 172 actuates a different latch fitting 162. Further, inembodiments having multiple latch fittings 162, one or more of the latchfittings 162 may not have a latch handle 182 coupled thereto. One ofskill in the art will appreciate that other variations in theconfiguration and location of the latch assembly 160 components arepossible without departing from the scope of the disclosed subjectmatter.

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

1. A latch assembly for a ramp assembly, the ramp assembly comprising aramp portion coupled to a fixed portion to reciprocate between a stowedposition and a deployed position, the latch assembly comprising: (a) alatch pin attached to the ramp portion; and (b) a latch fitting coupledto the fixed portion of the ramp assembly, the latch fitting comprising:(i) a hook portion; and (ii) a tang, wherein the latch fitting isselectively movable to reciprocate between a first position, in whichthe hook portion engages the latch pin to retain the ramp portion in astowed position, a second position, in which the hook portion isdisengaged from the latch pin, and a third position, in which the tangapplies a lifting force to the ramp portion.
 2. The latch assembly ofclaim 1, further comprising a latch handle rotatably coupled to thelatch fitting, the latch handle being rotatable between a retractedposition and an extended position.
 3. The latch assembly of claim 2,wherein the latch handle is at least partially disposed below an uppersurface of the fixed portion of the ramp assembly when the latch handleis in the retracted position.
 4. The latch assembly of claim 2, whereinthe latch fitting is manually rotatable from the first position to thesecond position by applying a force to the latch handle, the forcetending to rotate the latch handle toward the extended position.
 5. Thelatch assembly of claim 4, wherein the latch fitting is manuallyrotatable from the second position to the third position by applying aforce to the latch handle, the force tending to rotate the latch handletoward the extended position.
 6. The latch assembly of claim 2, whereinthe latch fitting is manually rotatable from the second position to thethird position by applying a force to the latch handle, the forcetending to rotate the latch handle toward the extended position.
 7. Thelatch assembly of claim 2, further comprising a biasing member forbiasing the latch handle toward the retracted position.
 8. The latchassembly of claim 1, wherein the tang travels upwardly along an arcuatepath to contact the ramp portion when the latch fitting moves from thefirst position to the third position.
 9. The latch assembly of claim 1,further comprising an actuator coupled to the latch fitting, wherein theactuator is selectively operable to reciprocate the latch fittingbetween the first position and the second position.
 10. The latchassembly of claim 9, further comprising a sensor for sensing a positionof the ramp portion.
 11. The latch assembly of claim 10, whereinoperation of the actuator is selectively interrupted according to theposition of the ramp portion.
 12. The latch assembly of claim 10,wherein a vehicle interlock is selectively engaged according to theposition of the ramp portion.
 13. A latch assembly for a ramp assembly,the ramp assembly comprising a ramp portion coupled to a fixed portionfor reciprocating motion between a stowed position and a deployedposition, the latch assembly comprising: (a) a latch pin coupled to theramp portion; (b) a latch fitting coupled to the fixed portion of theramp assembly, the latch fitting comprising: (i) a hook portion; and(ii) a tang; and (c) a latch handle coupled to the latch fitting, thelatch handle being movable to reciprocate between a retracted positionand an extended position, wherein the latch fitting is selectivelymovable to reciprocate between a latching position, in which the hookportion engages the latch pin to retain the ramp portion in a stowedposition, and a lifting position, in which the hook portion isdisengaged from the latch pin and the tang applies a lifting force tothe ramp portion.
 14. The latch assembly of claim 13, wherein the latchfitting is selectively movable from the latching position to the liftingposition by applying a force to the latch handle, the force tending tomove the latch handle toward the extended position.
 15. The latchassembly of claim 14, wherein the lifting force moves the ramp portionfrom the stowed position toward the deployed position.